After connecting the audio signal directly from the tape heads of an Otari MX5050 BII to a vintage Mcintosh C22 the performance was much less than anticipated. Have others experience this same disappointing result? Why is this audio path not favorable as compared to a path via the Otari built in preamp?

How will the Eros tape preamp perform given a direct signal from the Otari tape head and feeding the C22?

I don't know the gain or the EQ of the C22 tape head input. Those will be factors in how the circuit sounds. The sensitivity appears to be rated for a 2mV input, from which we can infer the gain should be about right for a 5050 playback head. I would guess that the EQ is NAB, so prerecorded NAB tapes should sound better than more recent IEC (e.g. Tape Project) tapes. The one flag for me is that the input impedance is 1 megohm. That seems like it is intended for old tape heads like early Ampex, which needed a high input impedance loading to prop up the treble response. The Otari head will probably be a lot more happy with something like a 90K load. The data I am reading states that one can adjust the phono preamp circuit by changing the input resistor but it does not mention if the tape head input is set up the same way. If the 1 meg is not easily removed and replaced with a 90K, one could emulate that 90K by putting a 100K resistor in parallel with the 1 meg. You might also need to experiment with the cables between tape head and preamp. They need to have a very low capacitance. And of course the playback head must be in good condition.

All that said I do suspect the Eros would probably sound better and it will offer the choice between NAB and IEC/CCIR playback EQs.